Where do we live? Part 2

In Part 1 we tried to imagine just how huge our galaxy is, to show where we live in this universe of ours. To accurately describe the universe beyond our galaxy we’re going to have to shrink the scale we used last time a hell of a lot more. Let’s take our already shrunk 6 million kilometre wide Milky way and pull it all the way down to 1 metre across. At this scale the Sun is 1.5 billionths of a metre across (half the width of DNA) and the Earth is 13.5 trillionths of a metre across (half the size of the smallest atom!). The entire galaxy now comfortably fits between your outstretched hands; hundreds of billions of stars, perhaps trillions of planets all between your fingertips.

The Large Magellanic Cloud

But our galaxy doesn’t sail through the universe alone, dotted around us are a number of satellite galaxies, there are around 25 smaller galaxies clustered around our own! The largest is called the Large Magellanic Cloud, on our scale it is a metre and a half from our galaxy (off to the side and slightly below). Home to billions of stars this 14 thousand lightyear wide galaxy would be the size of a pineapple on our little scale. The other galaxies surround ours in all directions with the closest 1 foot from our model and the furthest over 13 metres away, a real-world distance of over 1 million light years!

Even the Milky Way and her satellites are not alone, they are part of what we call the Local Group. Comprised of three major galaxies and dozens of satellites on our scale the local group is the size of a football pitch. Within these 10 millions lightyears lie trillions of stars, the largest galaxy is our nearest neighbour called Andromeda which itself contains well over 1 trillion stars. I always think fondly of Andromeda, as a child I had a book about the universe and I remember becoming upset because it told me that in 4 to 5 billion years the Milky Way and Andromeda are going to crash. Count to five……I’ll give you time to do it……we are now 600 kilometres closer! We are on a collision course with each other, on our scale Andromeda is 25 metres from us (2 and a bit buses) and its racing towards us at a rate of 5 billionths of a metre every year. Granted that doesnt scare me any more, but it’s going to be a titanic display!

In billions of years to come somebody will be voiding their no claims bonus...

Our Local Group may seem huge but it is tiny compared to some of the other groups nearby. 65 million light years away the Virgo Cluster is home to over 1 thousand galaxies! When we look at the Virgo Cluster now we’re seeing it as it was when the dinosaurs were walking the Earth, from the entirety of that point until now those photons have been serenely flying through space until one day after aeons of travel they land in our telescopes to tell us a tale from the deep past. The Virgo Cluster is so huge that we use it to name our local supercluster. Yes our Local Group is just a small part of a bigger group. The Virgo Supercluster contains at least 100 galaxy clusters and on our scale where the Milky way is a metre across and the Earth just half an atom wide it is over a kilometre wide. That’s about the same scale as an ant standing next to a car

Now I know this is beginning to sound repetitive but even our supercluster is just a tiny dot. When we look out beyond our supercluster we see that there are many, many more. Superclusters litter our universe forming truly colossal structures. They bunch together forming filaments (chains billions of lightyears long) and Great Walls formed from giant webs. This is our home. This is our universe. At this size our scale collapses again, with the Milky Way 1 metre wide some of these filaments would be tens of kilometres long!

One of the universe's 'Great Walls' made from filaments of superclusters

This is the observable universe, countless stars in hundreds of billions of galaxies. We are but a tiny part of this but it’s all out there! The numbers are horrible and the distances incomprehensible but I hope my analogy has helped. I was planning on taking this further and explaining just how small things in our universe can be but I found this brilliant animation that paints a picture worth a thousand blog posts. Its awesome, its unimaginably big, and its where we live.

Regarding the collision of two galaxies…even though they are “colliding”, statistically it’s very unlikely that everything will smash into each other destroying everything! A lot of people have the “OH SHIT THERES GONNA BE A MASSIVE EXPLOSION DESTROYING THE UNIVERSE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!” reaction (ok maybe I exagerated slightly…) but there’s so much space between stars that in most likelihood the stellar distribution will just get messed up due to gravitational effects.

Still going to be an impressive sight! Has anyone come up with an idea of what would happen if a star is swamped by dark matter? IIRC Andromeda has far more stars than us but the Milky Way is much more massive due to vast deposits of dark matter